The improvement in the impact strengths of polyamides is generally obtained by incorporation, in the form of a dispersed phase, of an impact modifier which exhibits an elastomeric nature and reactive functional groups (acrylic acid, maleic anhydride and the like) capable of reacting with functional groups of the polyamide matrix. This reactivity makes it possible to ensure a fine and homogeneous dispersion of the elastomer and a good adhesion at the nodule-matrix interface but results in a significant fall in the fluidity. This large change in the viscosity is harmful to the use, especially for fine or large-sized injected components.